Aluminum Alloys with Anodization Mirror Quality

ABSTRACT

The disclosure provides an aluminum alloy comprising second phase particles having an Al(FeMn)Si phase with an (Fe+Mn):Si ratio of 0.5 to 2.5 and a mean particle diameter of 0.5 μm to 10 μm. The disclosure also provides an aluminum alloy comprising 0.02 to 0.11 wt % Fe, 0 to 0.16 wt % Mn, 0 to 0.08 wt. % Cr, 0.40 to 0.90 wt % Mg, and 0.20 to 0.60 wt % Si, wherein the aluminum alloy is homogenized at a temperature from 550 to 590° C.

This patent application claims the benefit under 35 U.S.C. §119(e) ofU.S. Provisional Patent Application No. 62/014,546, entitled “AluminumAlloys with Anodized Mirror Quality,” filed on Jun. 19, 2014, which isincorporated herein by reference in its entirety.

FIELD

Embodiments described herein generally relate to aluminum alloys. Morespecifically, the embodiments relate to aluminum alloys with anodizationmirror quality for applications including enclosures for electronicdevices.

BACKGROUND

Commercial aluminum alloys, such as the 6063 aluminum (Al) alloy, areused for fabricating enclosures for electronic devices. The 6063 Alalloys and other 6000 series Al alloys contain iron and other alloyingelements. During alloy casting processing, primary iron(Fe)-containingsecond phase particles, such as Al₈Fe₂Si (α-AlFeSi phase) and Al₅FeSi(β-AlFeSi) particles, precipitate from the alloy. Iron-containingparticles conventionally have a mean diameter of several microns, andprovide grain-pinning for the polycrystalline bulk Al of the alloy. Inthe absence of grain pinning, the grain boundaries between the differentcrystals would be highly mobile during high-temperature processingsteps, resulting in rapid grain growth. This manifests in undesiredcosmetic defects such as mottling and orange peel.

These Fe-containing second phase particles also do not anodize. TheFe-containing second phase particles thereby reduce the quality of thepolished anodized surface of the Al alloy, and reduce mirror quality.There is a need to develop aluminum alloys having an improved mirrorquality when the surface is anodized to achieve a balance of sufficientgrain pinning and reduced anodization defects.

SUMMARY

The disclosure is directed to aluminum alloy compositions having reducedamounts of iron, optionally coupled with the addition of manganeseand/or chromium. Both manganese and chromium promote the formation ofα-AlFiSi particles. However, use of manganese and chromium can lead tocompositional micro-segregation, so the amount of them can be limited.The amounts of these elements can be in specific compositional ranges.The alloys can have smaller area fraction and/or mean particle size ofthe Fe-containing particles. This can result in improved mirror quality.Processing temperatures and methods are also disclosed.

In various aspects, the disclosed aluminum alloys have reduced Fecontent of 0.02 wt % to 0.16 wt % Fe. In some embodiments, the disclosedaluminum alloys have from 0.02 wt % to 0.12 wt % Fe.

In various additional aspects, the disclosed aluminum alloys includemanganese. In some embodiments, the alloy comprises 0-0.16 wt % Mn. Insome embodiments, the alloy comprises 0.02-0.06 wt % Mn. In someembodiments, the alloy comprises 0.04 wt % Mn.

In various additional aspects, the disclosed aluminum alloys includechromium. In some embodiments, the alloy comprises 0-0.08 wt % Cr.

In various additional aspects, Fe-containing particles in the aluminumalloys have an area fraction of less than 0.4%, and in some cases lessthan 0.25%. In further aspects, the mean diameter of iron containingparticles is less than 8 microns, and in some cases less than 4 microns.

In various embodiments, the alloy is a 6063 aluminum alloy.

In some embodiments, an aluminum alloy comprises 0.02 to 0.16 wt % Fe, 0to 0.16 wt % Mn, 0 to 0.08 wt % Cr, 0.40 to 0.90 wt % Mg, and 0.20 to0.60 wt % Si.

In some embodiments, a 6063 aluminum alloy comprises 0.10 to 0.12 wt %Fe, 0.02-0.06 wt % Mn, 0.40 to 0.90 wt % Mg, and 0.20 to 0.60 wt % Si.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification, or may belearned by the practice of the embodiments discussed herein. A furtherunderstanding of the nature and advantages of certain embodiments may berealized by reference to the remaining portions of the specification andthe drawings, which forms a part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be readily understood by the following detaileddescription in conjunction with the accompanying drawings, wherein likereference numerals designate like structural elements. The drawingsprovide exemplary embodiments or aspects of the disclosure and do notlimit the scope of the disclosure.

FIG. 1 depicts the reduction of constituent Fe-containing particlesbetween the baseline alloy (6063 Al alloy with 0.10-0.12 wt % Fe) andSample A (6063 Al alloy with 0.08 wt % Fe and 0.04 wt % Mn) disclosedherein, both in size and area fraction.

FIG. 2A depicts a bright field optical micrograph of anodization defectsfor the baseline aluminum alloy.

FIG. 2B depicts a bright field optical micrograph of anodization defectsfor Sample A.

FIG. 3 depicts the reduction of anodization defects between the baselinealloy and Sample A, both in size and area fraction.

FIG. 4 depicts the increases of gloss (20°), gloss (60°), anddistinctness of image (DOI) and the decrease in haze of anodized SampleA compared to the baseline alloy.

DETAILED DESCRIPTION

The disclosure may be understood by reference to the following detaileddescription, taken in conjunction with the drawings as described below.It is noted that, for purposes of illustrative clarity, certain elementsin various drawings may not be drawn to scale, may be representedschematically or conceptually, or otherwise may not correspond exactlyto certain physical configurations of embodiments.

The disclosure provides aluminum alloys that have improved mirrorquality after anodization than conventional aluminum alloys. In variousembodiments, the disclosed alloys comprise aluminum as the primary metaland iron, silicon, and magnesium as alloying elements. Optionally, thedisclosed alloys can further comprise manganese and chromium. The alloyscan also include copper, zinc, titanium, or other alloying elements toimpart various characteristics to the alloy. Exemplary aluminum alloysinclude, but are not limited to, 6000 series aluminum alloys, such as6063 aluminum alloys.

Without wishing to be limited to any theory or mechanism of action,β-AlFeSi particles can be converted to α-AlFeSi particles during thesolid-state homogenization treatment. This conversion can improveanodized surface quality. First, the shapes of α-AlFeSi particles canhave a lower aspect ratio than the often elongated shape of β-AlFeSiparticles. The sizes of round cosmetic defects, for example due to thedisruption of anodization process around the Fe-containing particles,can be set by the longest dimension of the particles. Hence, α-AlFeSiparticles with lower aspect ratio are more favorable than β-AlFeSi.Second, with lower ratio of Fe over Al chemical composition, α-AlFeSiparticles have lower phase fraction than β-AlFeSi particles, resultingin lower amount of anodization defects with α-AlFeSi particles. Theresulting surfaces achieve a balance of sufficient grain pinning andreduced anodization defects.

The aluminum alloy can be a casting alloy or a wrought alloy, either ofwhich can be heat-treatable or non-heat-treatable. Aluminum alloys arewidely used in engineering structure and components having light weightor corrosion resistance, such as the casings for consumer electronics.

The disclosed aluminum alloys include iron-containing (Fe-containing)second phase particles. Several Fe-containing intermetallic phases havebeen identified in second phase Fe-containing particles, depending onthe solidification conditions and alloy composition. The Fe-containingsecond phase particles can restrict grain growth during high temperatureprocessing, a process known as grain pinning. However, when anodized,the bulk aluminum in the alloy is oxidized while the micron-sizedFe-containing second phase particles are not, resulting in non-anodizedcosmetic defects that reduce the mirror quality of the anodized alloy.

The disclosed alloys reduce the area fraction and/or mean diameter ofthe Fe-containing particles while maintaining grain pinning capability.By reducing the area fraction of the Fe-containing particles, theunanodized surface area lacking mirror quality can be reduced, resultingin a promotion of visual gloss. Similarly, by reducing the mean diameterof Fe-containing particles, the unanodized surface area lacking mirrorquality can be reduced.

In various aspects, the disclosed aluminum alloys reduce the ironcontent below that of a conventional alloy. In further aspects, thealuminum alloys add a quantity of manganese and/or chromium to promoteα-AlFeSi Fe-containing particles, which are less detrimental to anodizedmirror quality than β-AlFeSi particles. In certain embodiments, thealuminum alloys can be homogenized at a temperature or temperatureswithin a specific range. Such alloys, when anodized, have improvedmirror qualities due to effective conversion to the more favorableFe-containing particles.

In certain embodiments, the aluminum alloy is a 6063 Al alloy.Conventional 6063 aluminum alloys can include Si from 0.2 to 0.6 wt %,Fe from 0.2 to 0.4 wt %, Cu of not more than 0.1 wt %, Mg from 0.45 to0.9 wt %, Cr of not more than 0.1 wt %, Zn of not more than 0.10 wt %,and Ti of not more than 0.10 wt %. Other alloying elements may each bepresent in not more than 0.05 wt %, and typically total no more than0.15 wt %. The balance of the alloy is aluminum.

In various aspects, the disclosure is directed to a modified 6063aluminum alloy having reduced Fe wt %. By reducing Fe content, the areafraction of Fe-containing particles is reduced, and the area fraction ofanodizable bulk aluminum is increased. In some variations, the aluminumalloys have reduced iron content to 0.2 wt % to 0.16 wt % Fe. In someembodiments, the disclosed aluminum alloys have from 0.10 wt % Fe to0.12 wt % Fe.

In certain variations, the modified alloy is a modified 6063 alloyincludes Fe from 0.02 to 0.16 wt %, Si from 0.2 to 0.6 wt %, Cu of notmore than 0.1 wt %, Mg from 0.40 to 0.90 wt %, Cr of 0-0.08 wt %, Zn ofnot more than 0.10 wt %, and Ti of not more than 0.10 wt %, with thebalance as aluminum.

In some embodiments, the disclosed alloys include less than or equal to0.3 wt % Fe. In some embodiments, the disclosed alloys include less thanor equal to 0.4 wt % Fe. In some embodiments, the disclosed alloysinclude less than or equal to 0.06 wt % Fe. In some embodiments, thedisclosed alloys include less than or equal to 0.08 wt % Fe. In someembodiments, the disclosed alloys include less than or equal to 0.10 wt% Fe. In some embodiments, the disclosed alloys include less than orequal to 0.12 wt % Fe. In some embodiments, the disclosed alloys includeless than or equal to 0.14 wt % Fe. In some embodiments, the disclosedalloys include less than or equal to 0.16 wt % Fe.

In some embodiments, the disclosed alloy has greater than or equal to0.02 wt % Fe. In some embodiments, the disclosed alloys include greaterthan or equal to 0.04 wt % Fe. In some embodiments, the disclosed alloysinclude greater than or equal to 0.06 wt % Fe. In some embodiments, thedisclosed alloys include greater than or equal to 0.08 wt % Fe. In someembodiments, the disclosed alloys include greater than or equal to 0.10wt % Fe. In some embodiments, the disclosed alloys include greater thanor equal to 0.12 wt % Fe. In some embodiments, the disclosed alloysinclude greater than or equal to 0.14 wt % Fe.

In some variations, Mn can be added to the alloy. The presence of Mnreduces the size of Fe-containing particles, thereby increasing theanodizable surface area of the alloy.

In some embodiments, the disclosed alloys include from 0 to 0.16 wt %Mn. In some embodiments, the disclosed alloys include from 0.02 to 0.06wt % Mn. In some embodiments, the disclosed alloys include less than orequal to or equal to 0.2 wt % Mn. In some embodiments, the disclosedalloys include less than or equal to or equal to 0.4 wt % Mn. In someembodiments, the disclosed alloys include less than or equal to or equalto 0.6 wt % Mn. In some embodiments, the disclosed alloys include lessthan or equal to or equal to 0.8 wt % Mn. In some embodiments, thedisclosed alloys include less than or equal to 0.10 wt % Mn. In someembodiments, the disclosed alloys include less than or equal to 0.12 wt% Mn. In some embodiments, the disclosed alloys include less than orequal to 0.14 wt % Mn. In some embodiments, the disclosed alloys includeless than or equal to 0.16 wt % Mn.

In some embodiments, the disclosed alloys include greater than or equalto 0.02 wt % Mn. In some embodiments, the disclosed alloys includegreater than or equal to 0.04 wt % Mn. In some embodiments, thedisclosed alloys include greater than or equal to 0.06 wt % Mn. In someembodiments, the disclosed alloys include greater than or equal to 0.08wt % Mn. In some embodiments, the disclosed alloys include greater thanor equal to 0.10 wt % Mn. In some embodiments, the disclosed alloysinclude greater than or equal to 0.12 wt % Mn. In some embodiments, thedisclosed alloys include greater than or equal to 0.14 wt % Mn.

In various additional aspects, the disclosed aluminum alloys includechromium. In some embodiments, the disclosed alloys include from 0 to0.1 wt % Cr. In some embodiments, the disclosed alloys include less thanor equal to 0.01 wt % Cr. In some embodiments, the disclosed alloysinclude less than or equal to 0.02 wt % Cr. In some embodiments, thedisclosed alloys include less than or equal to 0.03 wt % Cr. In someembodiments, the disclosed alloys include less than or equal to 0.4 wt %Cr. In some embodiments, the disclosed alloys include less than or equalto 0.05 wt % Cr. In some embodiments, the disclosed alloys include lessthan or equal to 0.06 wt % Cr. In some embodiments, the disclosed alloysinclude less than or equal to 0.07 wt % Cr. In some embodiments, thedisclosed alloys include less than or equal to 0.08 wt % Cr.

In some embodiments, the disclosed alloys include greater than or equalto 0.0 wt % Cr. In some embodiments, the disclosed alloys includegreater than or equal to 0.02 wt % Cr. In some embodiments, thedisclosed alloys include greater than or equal to 0.03 wt % Cr. In someembodiments, the disclosed alloys include greater than or equal to 0.04wt % Cr. In some embodiments, the disclosed alloys include greater thanor equal to 0.05 wt % Cr. In some embodiments, the disclosed alloysinclude greater than or equal to 0.06 wt % Cr. In some embodiments, thedisclosed alloys include greater than or equal to 0.07 wt % Cr.

In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt %Si, and 0.10 to 0.12 wt % Fe.

In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt %Si, and 0.08 wt % Fe.

In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt %Si, 0.08 wt % Fe, and 0.10 wt % Mn.

In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt %Si, 0.08 wt % Fe, and 0.04 wt % Mn.

In one embodiment, the aluminum alloy comprises 53 wt % Mg, 0.41 wt %Si, 0.02 wt % Fe, and 0.16 wt % Mn.

In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt %Si, 0.05 wt % Fe, and 0.12 wt % Mn.

In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt %Si, 0.08 wt % Fe, and 0.06 wt % Mn.

In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt %Si, 0.08 wt % Fe, 0.02 wt % Mn, and 0.04 wt % Cr.

In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt %Si, 0.08 wt % Fe, 0.04 wt % Mn, and 0.06 wt % Cr.

In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt %Si, 0.08 wt % Fe, 0.02 wt % Mn, and 0.08 wt % Cr.

In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt %Si, 0.11 wt % Fe, and 0.02 wt % Mn.

In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt %Si, and 0.11 to 0.12 wt % Fe.

The concentrations of Fe, Mn, and Cr can be selected to provide smalleraverage particle sizes and/or fewer second phase particles while stillproviding grain pinning during high-temperature processing of the Alalloy. The fine grain structure can be maintained to provide an anodizedmirror quality.

In some embodiments, the mean diameter of the Fe-containing particles isless than 9 microns. In some embodiments, the mean diameter of theFe-containing particles is less than 8 microns. In some embodiments, themean diameter of the Fe-containing particles is less than 7 microns. Insome embodiments, the mean diameter of the Fe-containing particles isless than 6 microns. In some embodiments, the mean diameter of theFe-containing particles is less than 5 microns. In some embodiments, themean diameter of the Fe-containing particles is less than 4 microns.

In some embodiments, the area fraction of the Fe-containing particles isless than 16%. In some embodiments, the area fraction of theFe-containing particles is less than 15%. In some embodiments, the areafraction of the Fe-containing particles is less than 14%. In someembodiments, the area fraction of the Fe-containing particles is lessthan 13%. In some embodiments, the area fraction of the Fe-containingparticles is less than 12%. In some embodiments, the area fraction ofthe Fe-containing particles is less than 11%. In some embodiments, thearea fraction of the Fe-containing particles is less than 10%. In someembodiments, the area fraction of the Fe-containing particles is lessthan 9%. In some embodiments, the area fraction of the Fe-containingparticles is less than 8%.

It will be appreciated by those of skill in the art that the amount ofother elements in the 6063 alloy can vary.

In some embodiments, the disclosed alloys include Mg from 0.45 to 0.9 wt%. In some embodiments, the disclosed alloys include Mg less than 0.9 wt%. In some embodiments, the disclosed alloys include Mg less than 0.5 wt%. In some embodiments, the disclosed alloys include Mg more than 0.45wt %.

In some embodiments, the disclosed alloys include Si from 0.2 to 0.6 wt%. In some embodiments, the disclosed alloys include Si less than 0.6 wt%. In some embodiments, the disclosed alloys include Si less than 0.4 wt%. In some embodiments, the disclosed alloys include Si more than 0.2 wt%. In some embodiments, the disclosed alloys include Si more than 0.4 wt%.

In some embodiments, the disclosed alloys include Cu from 0 to 0.1 wt %.In some embodiments, the disclosed alloys include Cu less than 0.1 wt %.In some embodiments, the disclosed alloys include Cu more than 0 wt %.

In some embodiments, the disclosed alloys include Zn from 0 to 0.1 wt %Zn. In some embodiments, the disclosed alloys include Zn less than 0.1wt %. In some embodiments, the disclosed alloys include Zn more than 0wt %.

In some embodiments, the disclosed alloys include Ti from 0 to 0.1 wt %.In some embodiments, the disclosed alloys include Ti less than 0.1 wt %.In some embodiments, the disclosed alloys include Ti more than 0 wt %.

In some embodiments, the aluminum alloys comprises 0.02 to 0.11 wt % Fe,0 to 0.16 wt % Mn, 0 to 0.08 wt. % Cr, 0.40 to 0.90 wt % Mg, and 0.20 to0.60 wt % Si.

In some embodiments, the aluminum alloy comprises 0.06 to 0.11 wt % Fe,0.02 to 0.06 wt % Mn, 0.40 to 0.60 wt % Mg, and 0.30 to 0.50 wt % Si.

It will be appreciated by those skilled in the art that other aluminumalloys besides 6063 aluminum alloys can be modified.

In some embodiments, the aluminum alloy is a 6000 series Al alloy, whichis defined by the presence of Mg and Si in the aluminum bulk material.In some embodiments, the aluminum alloy is a 6005 Al alloy. In someembodiments, the aluminum alloy is a 6005A Al alloy. In someembodiments, the aluminum alloy is a 6060 Al alloy. In some embodiments,the aluminum alloy is a 6063 Al alloy. In some embodiments, the aluminumalloy is a 6066 Al alloy. In some embodiments, the aluminum alloy is a6070 Al alloy. In some embodiments, the aluminum alloy is a 6083 Alalloy. In some embodiments, the aluminum alloy is a 6105 Al alloy. Insome embodiments, the aluminum alloy is a 6162 Al alloy. In someembodiments, the aluminum alloy is a 6262 Al alloy. In some embodiments,the aluminum alloy is a 6351 Al alloy. In some embodiments, the aluminumalloy is a 6463 Al alloy.

In other embodiments, the disclosed alloy can be a 6000 series Al alloy.6000 series Al alloys are alloyed with magnesium and silicon. Alloys ofthe 6000 series can be relatively easy to machine compared to other Alalloys, and they can also be precipitation hardened. In someembodiments, 6000 series Al alloys can include Si from 0.2 to 1.8 wt %,Fe from 0.1 to 0.7 wt %, Cu from 0.1 to 1.2 wt %, Mn from 0.05 to 1.1 wt%, Mg from 0.40 to 1.4 wt %, Cr of not more than 0.4 wt %, Zn from 0.05to 0.25 wt %, Ti of not more than 0.20 wt %, Bi of not more than 0.7 wt%, and Pb of not more than 0.7 wt %. In other embodiments,

In some embodiments, a melt for an alloy can be prepared by heating thealloy, including the composition, as described herein. After the melt iscooled to room temperature, the alloy can go through various heattreatments, such homogenization, extruding, forging, aging, and/or otherforming or solution heat treatment techniques as are known in the art.

In some embodiments, the cooled alloy can be homogenized by heating toan elevated temperature and holding at the elevated temperature for aperiod of time. Homogenization refers to a process in whichhigh-temperature soaking is used at an elevated temperature for a periodof time. It will be appreciated by those skilled in the art that theheat treatment condition (e.g. temperature and time) may vary. Invarious embodiments, the homogenization temperature for the aluminumalloys disclosed herein can range from about 550° C. to about 590° C. Inother embodiments, the homogenization temperature can range from about570° C. to about 580° C. In some embodiments, the homogenizationtemperature is above 550° C. In some embodiments, the homogenizationtemperature is below 590° C. The iron-containing particles are nothomogenized in solution.

Homogenation can occur from about 1 hour to about 6 hours, such as fromabout 2 hours to about 4 hours. In some embodiments, homogenization canoccur for less than 6 hours. In some embodiments, homogenization canoccur for less than 4 hours. In some embodiments, homogenization canoccur for more than 2 hours.

In some embodiments, the homogenized alloy can be hot-worked, e.g.,extruded. Extrusion is a process for converting a metal ingot or billetinto lengths of uniform cross section by forcing the metal to flowplastically through a die orifice.

In various aspects, the disclosed alloys can be anodized. Anodizing useselectrolytic passivation to increase the thickness of the natural oxidelayer on the surface of metal parts. Anodizing may increase corrosionresistance and wear resistance, and may also provide better adhesion forpaint primers and glues than bare metal.

Any of the Al alloys disclosed herein can be anodized. In particularembodiments, the Al alloy can be anodized to a depth of about 5 to about10 μm. In some embodiments, the disclosed alloy is anodized to a depthless than 10 μm. In some embodiments, the disclosed alloy is anodized toa depth greater than 5 μm. Aluminum is microscopically transparent, sothe non-anodized second phase particles can be seen through thealuminum, permitting an observer to see all particles in the volume ofthe anodized layer, not just the first surface.

In some embodiments, the disclosed alloys can form enclosures for theelectronic devices. The enclosures may be designed to have a blastedsurface finish, or absence of streaky lines. Blasting is a surfacefinishing process, for example, smoothing a rough surface or rougheninga smooth surface. Blasting may remove surface materials by forciblypropelling a stream of abrasive material against a surface under highpressure.

Standard methods may be used for evaluation of cosmetics includingcolor, gloss and haze. Gloss describes the perception of a surfaceappearing “shiny” when light is reflected. The Gloss Unit (GU) isdefined in international standards including ISO 2813 and ASTM D523. Itis determined by the amount of reflected light from a highly polishedblack glass standard of known refractive index of 1.567. The standard isassigned with a specular gloss value of 100. Haze describes the milkyhalo or bloom seen on the surface of high gloss surfaces. Haze iscalculated using the angular tolerances described in ASTM E430. Theinstrument can display the natural haze value (HU) or Log Haze Value(HU_(LOG)). A high gloss surface with zero haze has a deep reflectionimage with high contrast. DOI (Distinctness Of Image) is, as the nameimplies a function of the sharpness of a reflected image in a coatingsurface, based on ASTM D5767. Orange peel, texture, flow out and otherparameters can be assessed in coating applications where high glossquality is becoming increasingly important. The measurements of gloss,haze, and DOI may be performed by testing equipment, such as RhopointIQ.

By using the aluminum alloys of the disclosure, defects viewed throughthe anodized layer were reduced, providing a high gloss and highdistinctness of image with surprisingly low haze.

In some embodiments, the gloss (20°) of the anodized aluminum alloy isgreater than 160. In some embodiments, the gloss (20°) of the anodizedaluminum alloy is greater than 170. In some embodiments, the gloss (20°)of the anodized aluminum alloy is greater than 180. In some embodiments,the gloss (20°) of the anodized aluminum alloy is greater than 190. Insome embodiments, the gloss (20°) of the anodized aluminum alloy isgreater than 200. In some embodiments, the gloss (20°) of the anodizedaluminum alloy is greater than 210. In some embodiments, the gloss (20°)of the anodized aluminum alloy is greater than 220.

In some embodiments, the gloss (60°) of the anodized aluminum alloy isgreater than 135. In some embodiments, the gloss (60°) of the anodizedaluminum alloy is greater than 140. In some embodiments, the gloss (60°)of the anodized aluminum alloy is greater than 145.

In some embodiments, the DOI of the anodized aluminum alloy is greaterthan 80. In some embodiments, the DOI of the anodized aluminum alloy isgreater than 85. In some embodiments, the DOI of the anodized aluminumalloy is greater than 87.5. In some embodiments, the DOI of the anodizedaluminum alloy is greater than 90.

In some embodiments, the LogHaze of the anodized aluminum alloy is lessthan 600. In some embodiments, the LogHaze of the anodized aluminumalloy is less than 550. In some embodiments, the LogHaze of the anodizedaluminum alloy is less than 500. In some embodiments, the LogHaze of theanodized aluminum alloy is less than 450. In some embodiments, theLogHaze of the anodized aluminum alloy is less than 400. In someembodiments, the LogHaze of the anodized aluminum alloy is less than350. In some embodiments, the LogHaze of the anodized aluminum alloy isless than 300. In some embodiments, the LogHaze of the anodized aluminumalloy is less than 250. In some embodiments, the LogHaze of the anodizedaluminum alloy is less than 200.

EXAMPLES

The following examples describe in detail preparation andcharacterization of alloys and methods disclosed herein. It will beapparent to those of ordinary skill in the art that many modifications,to both materials and methods, may be practiced.

Example 1

A baseline alloy (6063 Al alloy with 0.10-0.12 wt % Fe) and Sample Aalloy (6063 Al alloy with 0.08 wt % Fe and 0.04 wt % Mn) were producedby vertical direct chill casting and extrusion into a thin profile. Thebaseline alloy was homogenized at a temperature between 560° C. and 580°C. Sample A was homogenized at a temperature of 580° C. FIG. 1 depictsthe data collected from backscattered secondary electron micrographs(SEMs) of ten images quantifying Fe-containing particles andmicrostructures in each alloy sample. The baseline alloy displayed anaverage particle Feret diameter of 2.4±0.2 μm and an average areafraction of 0.21±0.05%. Sample A displayed an average particle Feretdiameter of 2.25±0.15 μm and an average area fraction of 0.18±0.02%.Thus, the size and area fraction of constituent Fe-containing particleswere decreased between the baseline alloy and Sample A.

The baseline and Sample A alloys were also examined using bright fieldoptical microscopy, as depicted at FIGS. 2A & B. Using thesephotomicrographs, the anodization defects and dyed anodization werequantified. Specifically, the anodized layer is optically transparent.Thus viewing the sample from the top down through the anodization layerpermits one to quantify the defects through the entire thickness of theanodization layer. As shown at FIG. 3, the baseline alloy displayedsecond phase particles with a mean diameter of 9.5 μm and an areafraction of 16.5%, and Sample A displayed second phase particles with amean diameter of 5.5 μm and an area fraction of 8%. Thus, the size ofthe particles between the baseline alloy and Sample A decreased bynearly half, as did the area fraction.

The baseline and Sample A alloys were also examined for gloss (20°),gloss (60°), distinctness of image (DOI), and haze using agloss/DOI/haze meter based on the ASTM standards described herein. Asshown at FIG. 4, the baseline alloy had an average high glossmeasurement (gloss (20°)) of 150 GU, a medium gloss measurement (gloss(60°)) of 133 GU, a DOI of 76, and a haze of 650. In comparison, SampleA had an average gloss (20°) of 215 GU, a gloss (60°) of 143 GU, a DOIof 87, and a haze of 200. Thus gloss (20°), gloss (60°), and DOIincreased between Sample A and the baseline alloy. Surprisingly, thehaze of Sample A decreased relative to the baseline alloy.

Example 2

A series of sample alloys were prepared, and are depicted in Table 2.

TABLE 2 Modified 6063 Alloys containing 0.53 wt % Mg and 0.41 wt % SiIron wt % Manganese wt % Chromium wt % 0.10-0.12 wt % Fe     0.08 wt %Fe 0.08 wt % Fe 0.10 wt % Mn 0.08 wt % Fe 0.04 wt % Mn 0.02 wt % Fe 0.16wt % Mn 0.05 wt % Fe 0.12 wt % Mn 0.08 wt % Fe 0.06 wt % Mn 0.11 wt % Fe0.02 wt % Mn 0.08 wt % Fe 0.02 wt % Mn 0.04 wt % Cr 0.08 wt % Fe 0.04 wt% Mn 0.06 wt % Cr 0.08 wt % Fe 0.02 wt % Mn 0.08 wt % Cr

Having described several embodiments, it will be recognized by thoseskilled in the art that various modifications, alternativeconstructions, and equivalents may be used without departing from thespirit of the disclosure. Additionally, a number of well-known processesand elements have not been described in order to avoid unnecessarilyobscuring the embodiments disclosed herein. Accordingly, the abovedescription should not be taken as limiting the scope of the document.

Those skilled in the art will appreciate that the disclosed embodimentsteach by way of example and not by limitation. Therefore, the mattercontained in the above description or shown in the accompanying drawingsshould be interpreted as illustrative and not in a limiting sense. Thefollowing claims are intended to cover various generic and specificfeatures described herein, as well as statements of the scope of thepresent method and system, which, as a matter of language, might be saidto fall there between. Certain subject matter lying outside the scope ofthe claims can be claimed in future patent applications.

What is claimed is:
 1. An aluminum alloy comprising less than 16% areafraction of Fe-containing particles.
 2. The aluminum alloy according toclaim 1, wherein said alloy is a 6000 series aluminum alloy.
 3. Thealuminum alloy according to claim 1, wherein the alloy is a 6063aluminum alloy.
 4. The aluminum alloy according to claim 1, wherein saidalloy comprises from 0.2 wt % to 0.16 wt % Fe.
 5. The aluminum alloyaccording to claim 4, wherein the alloy is a 6063 aluminum alloy.
 6. Thealuminum alloy according to claim 1, wherein said alloy comprises from0.10 wt % to 0.12 wt % Fe.
 7. The aluminum alloy according to claim 1,wherein said alloy comprises from 0 to 0.16 wt % Mn.
 8. The aluminumalloy according to claim 1, wherein said alloy comprises from 0.02 to0.06 wt % Mn.
 9. The aluminum alloy according to claim 1, wherein saidalloy comprises from 0-0.08 wt % Cr.
 10. The aluminum alloy according toclaim 1, wherein said alloy comprises more than 0.02 wt % Cr.
 11. Thealuminum alloy according to claim 1, wherein said alloy comprisesiron-containing particles.
 12. The aluminum alloy according to claim 11,wherein the mean diameter of the iron-containing particles is less than9 microns.
 13. The aluminum alloy according to claim 12, wherein thearea fraction of the iron-containing particles is less than 16%.
 14. Thealloy of claim 1, wherein the gloss (20°) of the alloy is greater than160.
 15. The alloy of claim 1, wherein the gloss (60°) of the alloy isgreater than
 135. 16. The alloy of claim 1, wherein the DOI of theanodized aluminum alloy is greater than
 80. 17. The alloy of claim 1,wherein the LogHaze of the anodized aluminum alloy is less than
 600. 18.A method of processing a 6000 series aluminum alloy having less than 16%area fraction of Fe-containing particles, said method comprisinghomogenizing the alloy at a temperature from 550° C. to 590° C.
 19. Themethod of claim 18, wherein said homogenizing occurs for between 1 hourand 6 hours.
 20. A 6000 series aluminum alloy having less than 16% areafraction of Fe-containing particles, the alloy prepared by homogenizingthe alloy at a temperature from 550° C. to 590° C. for from between 1hour and 6 hours.